I'm tweaking a Debian live system (built with live-build), and I want it to boot straight into the system from syslinux — no menu, no timeout. According to the syslinux documentation, a timeout value of 0 means that the timeout is disabled, ie. it won't boot at all without user intervention, which is the opposite of what I want.

It might be nice to be able to hold down a key for those rare occasions where I do need to tweak the kernel line, but that's not essential. Really I just want an immediate boot. How do I get it?